Adaptive transfer of human T cells redirected against HBV results in reduced viral loads and induced immune responses in humanized mice

Effective T cell responses are essential to resolve HBV infection. However, in chronic hepatitis B patients HBV-specific T cell responses appear severely impaired. Adoptive transfer of T cells engineered to express an HBV-specific T cell receptor (TCR) may contribute to viral load reduction and reconstitution of HBV-specific immune responses. Aim of the study was to assess the engraftment capabilities and antiviral activity of HBV-specific redirected human effector T cells in vivo using HBV infected human liver chimeric uPA/SCID/ILγR2 (USG) mice. Methods: PMBCs isolated from healthy human blood were cultured for 1 week to activate and enrich the T cell population (+IL2 600 IU/ml; CD3 0.05 µg/ml). TCR-HBVs183 – 91 mRNA (restricted on MHC class I HLA-A201) was amplified by in vitro transcription and transduced via electroporation into activated T cells before being injected in uninfected or HBV-infected, haplotype matched (HLA-A201) or mismatched (HLA-A101) humanized mice. Virological markers and gene expression changes were determined by qRT-PCR and immunofluorescence. Results: One single injection of TCR transduced T cells in HLA-matched HBV infected mice already provoked a temporary reduction of viremia (median Δ0.5 log after 4 days), while multiple T cell injections (3 times in 12 days) resulted in progressive viremia reduction (median Δ1 log) exclusively in HLA-matched humanized mice, since viremia remained stable in similarly treated mismatched HBV-infected mice. Intrahepatic levels of HBV transcripts appeared 50% lower compared to controls and an increase of apoptosis markers (Caspase3) was detected in mice receiving TCR transduced cells, but not in controls. Also ALT levels and expression of human inflammatory cytokines and markers (e.g. IFNgamma, TNFalpha, IL-10, hTGFbeta, caspase8, granzyme B) were clearly enhanced in HBV-infected mice that received haplotype matched HBV-specific T cells, but not in mismatched controls. The successful reconstitution of mouse livers with human immune cells was also confirmed by the increased amounts of hCD8+ T cells (from day 6 to 12) detected by immunofluorescence in mouse livers. Conclusions: This pilot study aiming at exploring the potential of adoptive T cell therapy in chronic HBV infection using human liver chimeric mice indicates that repeated injection of TCR transduced human CD8+ T cells can induce a clear immune-mediated reduction of serological and intrahepatic viral loads without occurrence, at least for the time frame of investigation, of unspecific immune responses or graft versus host reactions.

Corresponding author: Kah, Janine

E-Mail: [e-mail]